hake/Config.hs.template: switch optimization level back to -O2
hake/Config.hs.template: switch optimization level back to -O2

-O3 enables loop unrolling which causes problems with thc, due to loops with
inline assembly being unrolled.

For example:
../usr/tests/thctest/thctest.c: Assembler messages:
../usr/tests/thctest/thctest.c:53: Error: symbol `_thc_cont_return_5' is already defined
../usr/tests/thctest/thctest.c:69: Error: symbol `_thc_cont_return_6' is already defined
../usr/tests/thctest/thctest.c:91: Error: symbol `_thc_cont_return_7' is already defined
../usr/tests/thctest/thctest.c:111: Error: symbol `_thc_cont_return_8' is already defined

mslovy/barrelfish,utsav2601/cmpe295A,8l/barrelfish,utsav2601/cmpe295A,kishoredbn/barrelfish,kishoredbn/barrelfish,kishoredbn/barrelfish,BarrelfishOS/barrelfish,linusyang/barrelfish,BarrelfishOS/barrelfish,8l/barrelfish,kishoredbn/barrelfish,mslovy/barrelfish,8l/barrelfish,BarrelfishOS/barrelfish,mslovy/barrelfish,8l/barrelfish,linusyang/barrelfish,mslovy/barrelfish,mslovy/barrelfish,linusyang/barrelfish,BarrelfishOS/barrelfish,utsav2601/cmpe295A,BarrelfishOS/barrelfish,8l/barrelfish,kishoredbn/barrelfish,BarrelfishOS/barrelfish,linusyang/barrelfish,BarrelfishOS/barrelfish,linusyang/barrelfish,mslovy/barrelfish,8l/barrelfish,BarrelfishOS/barrelfish,utsav2601/cmpe295A,kishoredbn/barrelfish,utsav2601/cmpe295A,utsav2601/cmpe295A,BarrelfishOS/barrelfish